#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
int fb(int x)
{
	if (x == 1 || x == 2)
		return 1;
	else
		return fb(x - 1) + fb(x - 2);
}
int main()
{
	int i = 0;
	scanf("%d", &i);
	int ret = fb(i);
	printf("%d", ret);
	return 0;

}
